There are most likely two clips that hold the battery in the car. They will be on either side of the battery near the bottom. You will have to loosen the bolts that hold them down. Then just unhook the positive and negative terminals and take the battery out.
On a side note you should invest in a battery maintainer of some sort. I use a battery tender jr. When batteries are allowed to discharge completely a few times, they don't last as long. As you can tell by your newish battery not taking a charge. Hope this helps
